1. Field of the Invention
The present invention relates to a trigger operated dispensing device, e.g. a trigger sprayer, for mounting on a storage container. This trigger sprayer includes a pumping mechanism to pump a desired amount of fluid out of the container for discharging the same for a certain application.
The pumping mechanism uses two operating cycles to pump a certain amount of fluid: the fluid ejection stroke and the fluid intake stroke. During the fluid intake stroke fluid is sucked from the container through an inlet flap valve into a pumping chamber. During the fluid ejection stroke, the fluid is pumped from the pumping chamber through an outlet flap valve, an outlet passageway and a discharge end of the dispensing device into the atmosphere.
2. Description of the Related Art
Heretofore, various trigger sprayers have been proposed. Some examples of these previously proposed trigger sprayers are disclosed in the following patents:
______________________________________ U.S. Pat. No. Patentee ______________________________________ 4,819,835 Tasaki 4,235,353 Capra et al. 4,618,077 Corsette 4,241,853 Pauls et al. ______________________________________
In the Tasaki U.S. Pat. No. 4,819,835 there is disclosed a trigger sprayer having a pumping mechanism including an inlet valve, an outlet valve, an intervalve chamber and a cylindrical collection chamber. A piston unit, in conjunction with a trigger and a spring are used to vary the volume of the collection chamber. A passageway connects the collection chamber with the intervalve chamber to establish a pressure balance between those chambers. The passageway between both chambers is fairly small, compared to the size of the chambers, and therefore the pressure balance between the chambers occur after the completion of an ejection stroke.
During the intake stroke, a vacuum is created within the collection chamber and communicates through the passageway to the intervalve chamber by moving the piston to increase the volume of the collection chamber. This vacuum forces an inlet ball valve open by lifting the ball to suck fluid from the container into the intervalve chamber and through the passageway into the collection chamber. During the fluid ejection stroke the piston is moved to decrease the volume of the collection chamber and to increase the pressure in the collection chamber and the intervalve chamber. This pressure lifts a fairly heavy exhaust valve body of the fluid outlet valve to open the outlet valve and to eject the fluid into the atmosphere.
In the Capra et al. U.S. Pat. No. 4,235,353 there is disclosed a trigger sprayer having a pumping mechanism including a piston chamber and an accumulating chamber. The pumping mechanism is operated to pump the fluid from the container into the accumulating chamber by sucking the fluid via an inlet ball valve into the piston chamber and, subsequently, by forcing the fluid through an inlet flap valve into the accumulating chamber. When pressure in the piston chamber is higher than the pressure in the accumulation chamber, the inlet flap valve is forced open for allowing the fluid to enter the accumulating chamber. The incoming fluid increases the pressure inside the accumulating chamber against a moveable wall and a spring mounted therein. An outlet opening of the accumulating chamber is closed by an outlet flap valve.
To dispense the fluid into the atmosphere, the operator has to press down on a discharge nozzle on a stem. The stem forces an outlet flap valve of the accumulating chamber open and the pressure and the spring biased piston inside the accumulating chamber pushes the fluid past the outlet flap valve into the atmosphere. As soon as the operator stops pressing down the discharge nozzle, the outlet flap valve is forced closed again.
In the Corsette U.S. Pat. No. 4,618,077 there is disclosed a pumping mechanism of a trigger sprayer including a pump chamber enclosed by a cylindrical member with an inner cone top. The cone top fits tight in a conical end wall and incorporates a normally closed check valve. The check valve is in the top part of the cone top and closes an inlet port within the conical end wall by touching the wall. An accumulation chamber is located between the conical end wall and the cylindrical member. A ring extending around the conical end wall and an annular flange on the outside of the cylindrical member seals an outlet port from the accumulation chamber to a discharge passageway in the trigger sprayer. A vacuum inside the pump chamber opens the check valve and allows the fluid to pass through the inlet port into the pump chamber. The pressure inside the pump chamber is communicated to and establishes a pressure in the accumulating chamber which results in the moving of the annular flange on the outside of the cylindrical member in an axial direction away from the ring extending around the conical end wall to allow the fluid to pass through the outlet port into the discharge passageway.
In the Pauls et al. U.S. Pat. No. 4,241,852 there is disclosed a trigger sprayer with a resilient bladder enclosing an accumulation chamber and a charging chamber enclosing a piston. The bladder has a relatively thin, flexible, forwardly projecting, cylindrical valve wall formed on the forward wall surface thereof and an annular radially inwardly directed flexible valve ring is formed substantially coplaner with the forward end wall surface of the bladder. The cylindrical valve wall is received in a rearwardly facing wall of the charging chamber. A vacuum in the charging chamber pulls the flexible valve ring against an extension of the cylindrical wall of the charging chamber to close it and lifts the far end of the cylindrical valve wall from its position in the rearwardly facing wall to create an opening towards the container to allow fluid to be sucked into the charging chamber. By establishing a pressure in the charging chamber the situation becomes reciprocated and fluid is moved into the accumulation chamber.
The pumping mechanism of the present invention including a pumping chamber and pressure controlled flap valves integrated therein is significantly different from the prior Takaki, Capra et al., Corsette and Pauls et al. pumping mechanisms described above.
As will be described in greater detail hereinafter, the pumping mechanism of the present invention with its single pumping chamber and pressure controlled flap valves associated therewith enhances the priming performance of the trigger sprayer significantly. Because of the close proximity of both flap valves associated with a back internal wall of the pumping chamber, the unusable dead volume in the pumping chamber is minimized. The small dead volume of the pumping chamber combined with the pressure controlled flap valves allows a quick pressure or vacuum increase to be established inside the pumping chamber during an ejection stroke or an intake stroke and minimizes the number of pre-pumping strokes required during priming of the trigger sprayer.